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Abstract

Interconnects for a fuel cell stack and methods of fabricating interconnects for a fuel cell stack that include a nitride layer over at least one surface of the interconnect.

Copyright

September 6, 2013

Country

United States

Language

English (United States)

This text was extracted from a PDF file.

This is the abbreviated version, containing approximately
6% of the total text.

Page 01 of 31

Attorney Docket No. 7917-513P

FUEL CELL INTERCONNECTS WITH NITRIDE LAYER AND METHODS OF MAKING THEREOF

[0001]BACKGROUND

[0002]In a high temperature fuel cell system, such as a solid oxide fuel cell (SOFC) system, an oxidizing flow is passed through the cathode side of the fuel cell while a fuel flow is passed through the anode side of the fuel cell. The oxidizing flow is typically air, while the fuel flow can be a hydrocarbon fuel, such as methane, natural gas, pentane, ethanol, or methanol. The fuel cell, operating at a typical temperature between 750ºC and 950ºC, enables the transport of negatively charged oxygen ions from the cathode flow stream to the anode flow stream, where the ion combines with either free hydrogen or hydrogen in a hydrocarbon molecule to form water vapor and/or with carbon monoxide to form carbon dioxide. The excess electrons from the negatively charged ion are routed back to the cathode side of the fuel cell through an electrical circuit completed between anode and cathode, resulting in an electrical current flow through the circuit.

[0003]In order to optimize the operation of SOFCs, the oxidizing and fuel flows should be precisely regulated. Therefore, the flow regulating structures, such as interconnects in the fuel cell system should be precisely manufactured.

[0004]SUMMARY

[0005]Embodiments include methods of fabricating an interconnect for a fuel cell stack that include providing a metal interconnect and annealing the interconnect in a nitrogen-containing environment to form a nitride layer over at least one surface of the interconnect.

[0006]In various embodiments, the method may further include forming a protective layer over the nitride layer on a first major surface of the interconnect. The protective layer may be a conductive oxide, such as a perovskite (e.g., lanthanum strontium manganite) or spinel (e.g., manganese cobalt oxide spinel) on the cathode-facing surface of the interconnect. The nitride layer may be a barrier layer that provides sufficient electrical conductivity while inhibiting oxygen from diffusing into the metal material of the interconnect during operation of a fuel cell stack. The nitride material of the barrier layer may optionally form in an interior portion of the

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Page 02 of 31

Attorney Docket No. 7917-513P

interconnect, such as within interstitial regions (e.g., pores) throughout the thickness of the interconnect.

[0007]In some embodiments, the interconnect may be a pressed-powder interconnect formed by compressing pre-alloyed particles including at least two metals in a powder press apparatus, such as a high-velocity compaction powder press apparatus, and the method may include incorporating the pressed-powder interconnect into a fuel cell stack. The interconnect may be annealed in a nitrogen-containing environment within the fuel cell stack to form the nitride layer. The annealing of the interconnect in a nitrogen-containing environment may be performed as p...